Purpose To determine the attachment and growth potential of 4 bacterial pathogens linked to hospital-acquired infections to various thermoplastic immobilization forms. Methods Four brands of heat-treated masks were inoculated with a known number of single bacterial species. Masks were sampled at 1-hour and 1-week time intervals. Bacterial colony counts were performed on these samples to determine initial attachment and survival capability. Ten radiation therapy clinics also were surveyed to determine current mask storage and usage conditions. Results Only gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis demonstrated an attachment capability at 1 hour, albeit greatly reduced (>99) from the initial inoculum. Neither gram-negative Escherichia coli nor Pseudomonas aeruginosa demonstrated any attachment capability to the same mask surfaces. No bacteria were recovered from any mask at the 1-week sampling interval. Discussion The considerable hydrophobic nature of the polycaprolactone material used in the construction of thermoplastic masks most likely prevents attachment of these bacteria when suspended in an aqueous (saline) solution. The addition of an antibacterial coating or incorporation of silver nanoparticles further reduces survival potential of these same bacteria. Preliminary results also indicate a substantial difference in gram-negative and gram-positive bacterial attachment capability. Conclusion The tested bacteria do not readily attach to or survive long on the forms used in this study. The composition of the mask material, when combined with low humidity and room temperature storage, suggest a reduced risk to radiation therapy patients for acquiring an infection with these particular bacteria during intermediate to long-term therapy. However, it does not suggest a complete elimination of microbe transmission from improper handling of stored forms. Health care personnel must exercise care when applying these masks to prevent low-level patient contamination.
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